Results: A new laser devised by researchers at Norfolk State University, Purdue, and Cornell is the smallest ever made: it consists of a nanoparticle just 44 nanometers in diameter. It can emit both photons and plasmons, which are waves that travel along the surface of metals.

Why it matters: The research is the first demonstration of a spaser, a device that some physicists believe will form the basis of future optical computers. Such computers have the potential to be much faster than today’s electronics, but current optical devices are bulky because photons are difficult to confine. Light in the form of plasmons can be confined to much tighter spaces, allowing for very fast, compact chips. Though researchers have previously made devices that can rout plasmons on chips, this spaser is the first device that can generate and amplify them.

Methods: To make the laser, the researchers coated a gold nanosphere with a layer of silica that’s embedded with dye. The gold provides the medium where the plasmons form; in the dyed silica layer, plasmons excited by light from a pumping laser are amplified, much as photons are amplified in the mirrored cavity of a conventional laser. The amplified plasmons then escape to travel along a metal surface, or they can be converted to photons so that the device emits a laser light. Either way, the device produces waves with the frequency of green light.

Next steps: The spasers could be improved by modifying them to emit different wavelengths. Spasers that work in the infrared, for example, might be useful for telecommunications.